Why idle before shut off?

[Mace Canute]

Bingo! This is the only need for idling an engine before shutdown. Even in the case of a liquid cooled engine that is very hot. Once it is shut down, where will the heat come from?

If you are running an engine hard and it is making lots of horsepower, you are burning lots of fuel/unit time. Certain spots in the engine are subjected to much higher heat than a lightly loaded engine, especially the exhaust valves, ports and manifold. If you don't idle for a few minutes to cool these hot spots down after working an engine hard, you do run the risk of warping a head or manifold, especially with the thin wall castings that are so popular wth manufacturers these days.

 

[zman007007]

I think by using the choke to kill the engine you would be washing off any oil that would have been left in the cylinder. In other words you would be starting with a dry cylinder next time you fire it up. zman :confused2:

 

[SPYDERLK]

Thanks for the quick replies. He doesn't just not let it idle , he shuts it off at full throttle, then starts it the same way. Drives me nuts....(easily done).

I think what youre describing is shutdown at High Idle. While this is full rpm it isnt really full throttle unless the engine is driving a heavy load. ... So altho not the best practice it isnt as bad as it may seem. I really dont like the startup at Hi idle setting tho because that actually is full throttle until the engine reaches the set rpm.
larry

 

[E/S]

I guess the answer is ;
To protect your investment.

E/S

 

[whodat526]

if it doesn't have a turbo and the thermostat is working u can shut it down after runnig it 24 hours in 100 degree weather hard and shut it right down because when the thermostat opens it will push the cool water in and the hot water back into the raidator it is not neccasary to let it idle before u shut it down i have ran many tractors and vechicles do u let your car are truck idle for a couple of minutes before u shut it down after u ran it down the highway for two are three hours i bet u dont and dont say there different because a motor is a motor and yes the tractor has just as much air going through the raidator as a car does because most tractor use a pushing fan which push more air than a pulling fan when goin down the road thats why tractors run at lower temps. then cars do

and i doubt anybody on here will set there and let there tractor cool completly down it would take hours because if u think about it diesel fires off of heat and compression not spark so once the motor is hot and the thermostat works it is never going to get hotter than the temp. rating on the thermostat are cooler than the temp. rating thats what it is there for to maintain a constent temp. if i am wrong then what is the thermostat on a tractor for in a car u could say for the heater but no cab no heater

 

[ray66v]

Synthetic oil should not be used in any motor during break in period.

Really?

Better tell General Motors to quit shipping brand new cars with synthetic oil in them.

 

[ray66v]

I think by using the choke to kill the engine you would be washing off any oil that would have been left in the cylinder. In other words you would be starting with a dry cylinder next time you fire it up. zman :confused2:

What? Where the heck did you get that idea?

 

[tungularafishcamp]

Interesting thread, if I don't let my sled cool down a minute or 2 after working it hard it backfires and as far as choking off it really helps for restart if your going to leave it overnight and it is really cold. Not sure what that has to do with tractors but I guess it carries over, always let my tractor and duramax for that matter cool down.
Rick

 

[harpoonalt]

;0Without overly complicating things, I'll stick with my routine of idle down , wait a minute , then shutoff. I'll leave my neighbor alone, let him do his thing and wait and see if anything happens. I'll be first to report if it does. This thread has giving me a lot to digest. So much so, I think I'll hop on the tractor and take a little ride to clear my head.

 

[RoyJackson]

if it doesn't have a turbo and the thermostat is working u can shut it down after runnig it 24 hours in 100 degree weather hard and shut it right down because when the thermostat opens it will push the cool water in and the hot water back into the raidator it is not neccasary to let it idle before...

However, the coolant flows stops once the engine is shut down and the thermostat had been open since the engine got to operating temperature.
So, you still have the heat sink situation.
As far as my road vehicle, I don't run the engine hard except when merging on to a highway. Even then, I shift (manual transmission) 1000-2000 RPM below redline. So, it doesn't really get that hot...and ambient (outside) temperature doesn't affect the operating temperature of an engine too much.

At this point, I'd say the guys who shut down immediately will continue to do so..and the guys who idle for a few minutes will also continue to do so. Furthur posts (n this thread) will likely be reiterations of earlier posts.
Not too much use continung...